The present invention relates to an actuator including a carriage having a head and rocking about a rotary shaft, in a disk unit such as, for example, a magnetic disk unit.
In a disk unit such as a magnetic disk unit, a carriage provided with a head is required to have excellent dynamic characteristics in order to get access to a target track accurately at a high speed.
FIG. 8 is an exploded perspective view of a conventional actuator for a disk unit or the like. FIG. 9 is a plan view of the carriage of FIG. 8, and FIG. 10 shows the Xxe2x80x94X section of FIG. 9.
In FIG. 8, magnets 15 are respectively fixed to upper and lower yokes 9A, 9B. The yokes 9A, 9B are secured by shafts 16 with a specified space there between in a manner such that magnets 15 are opposed to each other in reverse polarity. A coil 7 is fixed on one end of a carriage 8, and on the other end is located a suspension 6 which supports a head 5 for signal recording and reproducing. The carriage 8 is supported by a rotary shaft (not shown) which is set through bearing 36 so that the coil 7 is positioned inside the space and able to rotate about the rotary shaft. That is, when the coil 7 is supplied with a current, a driving force is generated in the coil 7 according to the Fleming""s rule, and thereby, the carriage 8 makes a rocking motion.
In a conventional actuator as described above, examples of configuration with the coil 7 fixed on the carriage 8 are shown in FIG. 9 and FIG. 10. In these figures, projection 17 for securing the coil 7 is integrally disposed beforehand at the end of the carriage 8, and the projection 17 and the coil 7 are secured by means of holding member 11 made up of thermoplastic resin.
However, in such conventional configuration, since the coil 7 is supported in a cantilever fashion by the carriage 8, it is not possible to obtain sufficient strength and rigidity for the installation. As a result, the resonance frequency of the carriage 8 becomes lowered and it is unable to satisfy the requirement for higher performance of the disk unit.
FIG. 11 and FIG. 12 are perspective views showing other examples of configuration with respect to the carriage 8 and the coil 7. FIG. 11 is a perspective view before assembly of the carriage 8 and the coil 7. FIG. 12 is a perspective view after assembly of the carriage 8 and the coil 7. In FIG. 12, the portion shaded by black spots is the support member 11 made up of resin. FIG. 13 shows the XIIIxe2x80x94XIII section of FIG. 12. FIG. 14 shows the XIVxe2x80x94XIV section of FIG. 12.
In FIG. 11, a long plate-form projection 13 is formed at the inside of coil fitting arm 12A of the carriage 8. Also, there are provided three through-holes 14 at the boundary between the bottom portion of projection 13 and the arm 12A. The configuration of coil fitting arm 12B is same as that of the coil fitting arm 12A. The carriage 8 and the coil 7 are set in a metallic mold (not shown), and the coil 7 is positioned with reference to the carriage 8, and holding member 11 made up of thermoplastic resin is filled therein. Thus, the coil 7 is fixed on the carriage 8. FIG. 12 is a perspective view of the coil 7 fixed on the carriage 8. Like the XIIIxe2x80x94XIII section of FIG. 12 shown in FIG. 13, the through-holes 14 are filled with resin of the holding member 11, and therefore, the coil 7 will be free from slipping off from the arms 12A, 12B in the direction of arrow X in FIG. 12. Also, like the XIVxe2x80x94XIV section of FIG. 12 shown in FIG. 14, the projection 13 bites into the holding member 11, and the holding member 11 bites into the depression 7A of winding of the coil 7 as well. Accordingly, the coil 7 is sufficiently held in the direction of arrow Y against the arms 12A, 12B. By such configuration, the portion of fitting the arms 12A, 12B and the coil 7 can be made nearly equal in thickness to the arms 12A, 12B. Since the coil 7 can be disposed between two strong arms 12A and 12B, the resonance frequency will become higher and it is possible to meet the requirement for higher performance of the disk unit.
However, with the recent improvement in performance of disk units, there is an increasing demand for smaller and thinner disk units. To make the disk unit further thinner, it is necessary to reduce the entire actuator less in thickness. For achieving the purpose, it is necessary to make the yokes 9A, 9B, and magnet 15 thinner, and also to reduce the thickness t see FIG. 14) of arms 12A, 12B and coil 7 as much as possible. However, if the thickness t of the arm 12A shown in FIG. 14 is reduced, it will become difficult to form the projection 13 in the center of arm 12A.
The present invention is intended to solve the above problem, providing an actuator wherein the coil may be secured with a sufficient strength against the carriage even in case the coil fitting arm is reduced in thickness.
The actuator of the present invention has the following configuration.
In this configuration, there are provided a pair of yokes opposing to each other via the first specified space, a magnet fixed to at least one of the yokes, and a carriage holding a coil on one end thereof against the magnet via the second specified space and rocking about a rotary shaft; and the carriage comprises two coil fitting arms opposing to each other having stepped portions respectively formed on the opposing surfaces and at least one through-hole, piercing from the bottom to the top of the stepped portion, whose size is larger at the bottom than at the top thereof, the coil disposed between these two coil fitting arms, and a holding member for securing the coil fitting arms, the through-hole and the coil. The holding member is preferable to be formed of a resin-filled block.
By this configuration, since each of the coil fitting arms is provided with a stepped portion, the coil may be securely fixed on the arms even in case the arms are reduced in thickness. Also, there are provided through-holes at the stepped portion of the arm, and the through-hole area is larger at the bottom of the stepped portion than at the top thereof. Also, resin is filled into these through-holes to secure the coil, and the resin will free from slipping off from the holes, and thereby, the coil can be completely fixed on both arms.